MORTGAGE LOANS - Impaired Loans (Details) - Commercial mortgage loans - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Recorded Investment
With no related allowance recorded	$ 83	$ 0
With an allowance recorded	9,445	5,684
Unpaid Principal Balance
With no related allowance recorded	83	0
With an allowance recorded	9,305	5,309
Related Allowance
With an allowance recorded	2,481	1,296
Average Recorded Investment
With no related allowance recorded	83	0
With an allowance recorded	3,148	1,895
Interest Income Recognized
With no related allowance recorded	0	0
With an allowance recorded	184	267
Cash Basis Interest Income
With no related allowance recorded	0	0
With an allowance recorded	$ 217	$ 293

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